How did the cannon on the west side of Jian 'ou dialect come from?

Jian 'ou is an important military and political town in ancient times. One year, Jianzhou bought several heavy guns and put them at the city gate. Although it is exposed to the sun and rain, it is also safe. Later, when the foreign enemy attacked and attacked the city gate, the cannon misfired.

Describe the critical moment when the chain was broken. Over time, it has become a dull and stupid reference.